KR100870597B1 - A process for manufacturing poly(latic acid) bio-composites and poly(latic acid) bio-composites thereby - Google Patents

Abstract

A method for manufacturing polylactic acid bio composite material is provided to produce a polylactic acid bio composite material by adopting a compression molding using a carding process. A method for manufacturing polylactic acid bio composite material comprises a step for preparing the web by blending fabric through a carding process by selecting substrate polymer the polylactic acid(PLA) fiber and natural fiber as reinforcing material; a step for making the mat by pre-loading the web; and a step for manufacturing by compressing and molding the bio composite plate mat. In a step for preparing web, the web is prepared by replacing some of polylactic acid fiber with the polypropylene fiber. The replaced polypropylene fiber forms 15~35 weight% among the web total weight.

Description

A process for manufacturing poly (latic acid) bio-composites and poly (latic acid) bio-composites thereby

 The present invention provides a method for producing a biocomposite material, in particular, polylactic acid (PLA) fiber, which is a biodegradable polymer fiber, and optionally, a general-purpose polymer polypropylene fiber and a natural fiber by mixing and compression molding according to a carding process. The present invention relates to a PLA biocomposite manufacturing method and a PLA biocomposite accordingly, which solve the problems of lactic acid biocomposite manufacturing.

Recently, as environmental awareness is increasing and global regulations on environmental issues such as waste plastic treatment, climate change agreements, and new environmental laws and regulations are gradually strengthened, bio-composites are new materials that are more environmentally friendly. There is an active research on. Biocomposites are polymers made from natural flours such as cellulose-based wood flour, rice hull powder, and bamboo powder, and natural fibers such as wood fibers, wood flour, hemp, and ramie as reinforcements. As a composite material, it is mainly used as a substitute for a polymer composite material using carbon fiber and glass fiber, which are inorganic raw materials. The advantage of such a biocomposite is that it is biodegradable unlike conventional inorganic fillers and thus has the advantage of being environmentally friendly.

Most of the biocomposites currently being used or researched are added to the polyolefin (PP, PE, PS) -based polymers, which are currently used in the polymer industry, as natural deck or natural powder, which is a kind of environmentally friendly biodegradable filler. It is being used and used, and it is also practically used or developed for structural materials, packaging materials and automobile interior materials. However, the use of such polyolefin-based materials as substrates can be said to be partly environmentally friendly, but it is not possible to say that they are completely environmentally friendly because the substrates are non-degradable. Therefore, in the future, biocomposites using biodegradable polymers, which are fully biodegradable and environmentally friendly materials in nature, are expected to be used in industrial fields. Is going on.

Among the biodegradable polymers, polylactic acid (PLA, poly (latic acid)) is noted. When biodegradable PLA is used as a biocomposite substrate polymer, it is noted that it is a sustainable biological resource that can replace depleted petroleum resources in addition to its environmentally friendly advantages because it is decomposed into non-toxic substances even when used after landfilling. However, since the PLA fiber is very brittle at room temperature, there is a problem when manufacturing a biocomposite material by conventional injection molding. In other words, bio-composite materials are easily broken when Young's modulus is manufactured by injection-molding higher natural fillers, and in addition, there is a problem due to the brittleness and the powder processing of natural materials required for injection molding. .

The present inventors propose a compression molding using a carding process in order to solve the problems caused by conventional injection molding when manufacturing a biocomposite material using such PLA fibers as a substrate polymer. Furthermore, in order to overcome the brittleness of PLA and provide biocomposites with good physical properties, PP composites, which are general-purpose polymers, are mixed together to produce biocomposites by compression molding, which satisfy various indices required for biocomposites. Material could be prepared.

One object of the present invention is to prepare a biocomposite material in which PLA brittleness is overcome by compression molding using a carding process. In addition, another object of the present invention, according to compression molding using a carding process, to replace a part of the PLA fiber with a general-purpose polymer PP to produce a biocomposite material having better physical properties. Another object of the present invention is to provide a biocomposite material that can be applied to the electronics case and automotive interior materials industry, as well as various industrial applications requiring mechanical strength.

The present invention is to prepare a web (web) by mixing the PLA through the carding process by selecting PLA as a substrate polymer, a natural fiber as a reinforcing material, to prepare a mat by pre-loading the web, and to compress and mold the mat The biocomposite manufacturing method comprising the steps of manufacturing the biocomposite plate (plate) to overcome the PLA brittleness, it is possible to produce a biocomposite material that can have an indicator within the required tensile, bending and impact strength range.

In addition, the manufacturing method according to the present invention is a very useful invention that can produce a biocomposite material that can achieve a sufficient strength and biodegradability even by replacing a portion of the PLA fiber with PP fiber. Biocomposite material according to the present invention is a certain mechanical property is maintained, it is possible to various applications in industrial fields such as electronic products, automotive interior materials.

In order to achieve the above object, a method of preparing a web by mixing PLA through a carding process by selecting natural fibers as PLA and a reinforcing material as a substrate polymer, and preparing a web by preloading the web And a method for producing a biocomposite material comprising compressing and molding a mat to produce a biocomposite plate.

In addition, the present invention is to replace the part of the PLA with PP to prepare a web (web) by mixing the fiber through a carding process by selecting PLA and PP, a natural fiber as a substrate polymer, a reinforcing material, pre-loading the web mat ) And a method of manufacturing a biocomposite material, which comprises a step of manufacturing a bio-composite plate by compressing and molding the mat.

It was confirmed that the biocomposite according to the above manufacturing method can overcome the PLA embrittlement and have an index within the tensile, bending and impact strength ranges required for the biocomposite.

DETAILED DESCRIPTION Hereinafter, the present invention will be described in detail, but for the purpose of illustration, it is not intended to limit the scope of the invention. First, the components of the biocomposite according to the present invention will be described, and the composite materials and experimental examples according to the present invention to which the present invention is applied will be described. The carding process referred to throughout this specification is also referred to as a normal carding process, which completely removes miscellaneous or very short fibers by separating the fibers that are aggregated into small chunks, and separates the fibers one by one so that they are aligned in parallel. It is defined as a process of collecting, collecting and slicing this into a sliver, and can be worked with a conventional carding or carding machine.

The biodegradable polymer selected in the present invention was poly (lactic acid) (PLA), and a fibrous material was used. The length was 30mm, the melt index was 10-30g / 10min (190 ℃ / 2160g) and the density was 1.22g / cm ³ . Formula 1 shows the chemical structure of PLA.

Meanwhile, polypropylene (PP) fibers purchased from Kolon Co., Ltd. were used as materials used as non-degradable polymers to replace a part of PLA. PP fibers had a density of 0.91 g / cm 3 and MFI 12 g / 10 min (230 ° C./2160 g) with a fiber length of 30 mm.

In the present invention, natural fibers such as kenaf and jute fibers (purchased from Suyoung Co., Ltd.) were used as reinforcement materials of PLA and, optionally, PP fibers, and biocomposites, without being limited thereto. Natural fibers within a length of 50 to 70 mm can be used.

Example 1 Preparation of PLA Biocomposite Material

The PLA biocomposite was molded through the compression and molding of the following steps. First, carding machines were used to blend the biodegradable polymer fibers, PLA fibers and / or non-degradable polymer PP fibers, and kenaf or jute fibers. The mixed web was punched with a needle punch, and then preloaded at 120 ° C. to prepare a mat, and the produced mat was subjected to compression molding. The compression temperature was 200 ℃ and the pressure was 70kgf / cm ² . Through this process, a bio composite plate was manufactured. The plate was stored in a polyethylene bag to prevent the penetration of moisture. 1 shows a manufacturing process of the biodegradable PLA biocomposite through the carding process. In addition, Table 1 summarizes the mixing ratio of the manufactured biocomposites. Hereinafter, the mixing ratio is expressed in weight percent.

Table 1. Biocomposite Mixing Ratio (wt%)

Experimental Example 1 Specimen Preparation

The dried plate was fabricated in a tensile strength test specimen and a flexural strength test specimen at room temperature and 5 MPa through a punching process for fabrication. The fabricated specimens were humidified for 40 hours at a temperature of 23 ± 2 ℃ and a relative humidity of 50 ± 5%.

Experimental Example 2 Tensile Strength Measurement of Biocomposites

Tensile strength was measured to evaluate the effect on the tensile strength of biocomposites according to the carding process and the type of substrate polymer. Measurements were made using a Universal Testing Machine (Zwick Co.) according to ASTM D638-03. At this time, the tensile speed was measured at room temperature as 5mm / min and the tensile strength value was calculated as the average value of five samples.

Experimental Example 3 Measurement of Flexural Strength of Biocomposites

The flexural strength was measured to evaluate the effect on the bending strength of biocomposites according to the carding process and the type of substrate polymer. It was measured using a Universal Testing Machine (Zwick Co.) according to ASTM D790-03. At this time, the compression rate was measured at room temperature of 5mm / min and the tensile strength value was calculated as the average value of five samples. Figure 2 shows the three-point bending test method.

Experimental Example 4 Impact strength measurement of biocomposites

Impact strength is the value obtained by dividing the energy required to break a material by load by the unit area or per unit width of the material. Impact strength in ASTM D256 is expressed as the value divided by the width of the impact surface. Measuring method is to measure in the direction of scratches on the main part of the specimen. (Notch) How to measure in the opposite direction to the scratch (un-notch) The force consumed to destroy the plastic specimen by putting it vertically and impacting the upper part. It is one of the most important items in the testing of mechanical properties of polymer composites. Impact strength was tested using the Notched method.

1. Tensile strength according to the type of biocomposite

Figure 3 shows the tensile strength values of PP and natural fibers, PLA and jute fiber biocomposites. First, in the case of a biocomposite made of natural fibers and PP, it was confirmed that the tensile strength value of the biocomposite decreases according to the content of the natural fiber. Although the tensile strength of biocomposite decreased slightly until the first 30%, in the case of biocomposite containing a large amount of natural fiber, the tensile strength value was greatly reduced. It was found that the tensile strength of the biocomposite was greatly reduced by weakening the bond between and the natural fiber. In addition, the reason is that the increase in the content of the natural fiber in the biocomposite increases the content of the voids in the biocomposite, the tensile strength value is lowered. This can be confirmed through the following Table 2. The biocomposite material showed a result of increasing the pore content as the natural fiber content increased. The voids decreased the tensile strength values because they prevented the bond between PP and jute fibers and the transfer of stress. The content of the pores also includes pores at the interface and pores in the lumen in natural fibers. Bio-composites using PLA as substrate polymers showed surface cracks during the production of bio-composite specimens with low natural fiber content due to the brittle nature of PLA, resulting in low strength of the composites. On the other hand, 50% and 70% biocomposites containing a large amount of natural fiber showed higher strength. In addition, it showed relatively better tensile strength than biocomposites containing only PP as substrate polymer. This result may be one reason for selecting PLA polymer as substrate polymer of biocomposite.

Table 2. Pore Content According to Natural Fiber Content in Jute / Polypropylene Composites

4 shows the tensile strength value according to the type of substrate polymer of the biocomposite. Substrate polymer was used as a mixture of PP, PP and PLA, and PLA (Type 1: PP fiber 50% + Jute fiber 50%, Type 2: PP fiber 35% + PLA fiber 15% + Jute fiber 50%, Type 3 : PP fiber 25% + PLA fiber 25% + Jute fiber 50%, Type 4: PP fiber 15% + PLA fiber 35% + Jute fiber 50%, Type 5: PLA fiber 50% + Jute fiber 50%). Except for the slight decrease in tensile strength only in Type 5, which used PLA alone as the substrate polymer, the strength value of the substrate polymer was not significantly reduced and showed similar tensile strength values. This indicates that even though replacing part of the substrate polymer PP with PLA, there is no effect of tensile strength value.By replacing bio-materials with PLA, the biodegradability is high. It may be used as a material.

As a result, the PLA biocomposite manufactured by compression molding using the carding process was able to solve the problems caused by the brittleness of the material, compared to the case produced by injection molding, and part of the PLA fiber was replaced by PP fiber. Even if it appears to possess sufficient physical properties.

2. Flexural strength according to the type of biocomposite

As a result of measuring the bending strength of the biocomposite prepared in Example 1, it was shown in FIG. 5. Biocomposites using mixed substrate polymer of PP and PLA showed little difference in strength by mixing PP and PLA even when 50% of Jute fiber was filled. This indicates that not only the PLA fiber is applied but also the mixed substrate polymer of PP can be sufficiently used as the substrate polymer of the biocomposite.

3. Impact strength according to the type of biocomposite

Referring to FIG. 6, the impact strength value increased as the content of the natural fiber in the biocomposite material increased. The improvement in impact strength indicates that the biocomposites have overcome the brittleness of the substrate polymer. Impact strength using mixed substrate polymers is shown in FIG. 7. As a result of mixing PP and PLA by the ratio and using the substrate polymer as a biocomposite of jute fiber, the PP and PLA mixed polymer showed sufficient impact strength.

1 shows a schematic process diagram of manufacturing a biocomposite material according to the present invention,

Figure 2 illustrates a method for measuring the bending strength of the biocomposite material according to the present invention,

3 is a tensile strength measurement according to the type of substrate polymer and the content of natural fiber,

4 is a tensile strength measurement of the biocomposite according to the type of substrate polymer,

5 is a measurement of the bending strength of the biocomposite according to the type of substrate polymer,

6 is an impact strength measurement according to the type of substrate polymer and the content of natural fiber,

7 is a measurement of impact strength of biocomposites according to the type of substrate polymer.

Claims (4)

Preparing a web by mixing the polylactic acid (PLA) fiber as a substrate polymer and natural fiber as a reinforcing material and mixing the same through a carding process; Preloading the web to produce a mat; And In the method for producing a polylactic acid biocomposite, comprising the steps of pressing and molding a mat to produce a bio-composite plate, In the preparing of the web, a web is prepared by replacing a portion of the polylactic acid fiber with polypropylene fiber, wherein the polypropylene fiber is 15 to 35% by weight based on the total weight of the web. Polylactic acid biocomposite production method. delete The method for producing a polylactic acid biocomposite according to claim 1, wherein the natural fiber is kenaf or jute fiber. A polylactic acid biocomposite produced by the method according to any one of claims 1 to 3.

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